1. Field of the Invention
This invention relates to data processing systems and more particularly to the recovering and storing of status signals used in data communications.
2. Description of the Prior Art
Highly flexible and cost effective communications subsystems have been provided for coupling data processing systems to communication channels, such as those associated with a publicly accessible (e.g., telephone) communications network. Such systems have been embodied in hardware/firmware architectures which respond to commands from a communication processor associated with a central processing unit and enter into either a receive mode, a transmit mode, or concurrent transmit/receive modes for transferring data messages between the communication processor and the communication channel. Data transfers occur under the control of a firmware system acting in concert with a microprocessor within the adapter to assemble and disassemble whole or partial data bytes of varying bit sizes. System architectures which have been used readily accommodate an expansion of capacity and exhibit dynamic flexibility.
Typical of such communications systems are the ones described in U.S. application Ser. No. 000,304 entitled, "Hardware for Extending Microprocessor Addressing Capacity," now abandoned, and U.S. application Ser. No. 053,110 entitled, "Communication Line Adapter for a Bit and Byte Synchronized Data Network," now abandoned.
However, these systems required an excessive number of microinstructive steps to control the direct connect clock control signals, the clear to send signals, and the protocol signals for each communication line coupled to the communications subsystem. This created excessive firmware overhead with a resulting reduction in communications subsystem throughput.
It should be understood that the references cited herein are those which the applicants are aware of, and are presented to acquaint the reader with the level of skill in the art, and may not be the closest reference to the invention. No representation is made that any search has been conducted by the applicants.